I Need Professional Help About ?

I am 23 years old & I have so much stress about a big test coming out , usually I don’t have stress about things in my life but this time no matter what I do , I can’t cope with it because
about 6 months ago, I had this exams & I failed because teacher wasn’t expert enough to teach me correct material & because of that & after studding so much hard (about 6 mounts)& pay a lot of money for class & test, I failed …….. I was so depress & I was in shock because I studied well & my teacher thought that I could pass the test with high score…..anyway……
After that, I found professional teacher & from that time on, I am studding so hard with his method & my new teacher believe I am doing very well & he also believe I can achieve high score on test…
Now, it is only 20 days left to my big test & I should really pass it this time ….
but the problem is that I have so much stress(even I can’t sleep at nights) & I feel ,I can’t do it this time too & I will be fail again, I don’t believe in myself & I have no confidence & I also don’t believe in my teacher when he say I can pass, when I imagine the day which I have test or the day which I will receive my score, a big fear , a big failure fear takes over me & then I feel so much stress, even I hear my fast heart beat……
I know that I cannot pass the test with stress & anxiety ….. & no matter what I do I can’t get rid of it….
I talk to different people; I think about it, I tried to make it simple for myself….
I keep saying to myself : I can do this , this time is different , I will pass the test … why should I have stress ??
Uhh, I know, I can only help myself & I am sure I can pass the test only if I haven’t stress & anxiety…
What should do? How I can cope this feeling? Please help??
Thanks